Feature: Pin a specific `nginx` tag

[felixscheinost]

Description of the change

Currently nginx:alpine is used which is bad practice, as the image will never be updated after the initial pull. I suggest that rather a specific nginx version should be used, which would be updated regularly.

Benefits

• Users wouldn't need to manually check of updates of nginx and manually overwrite the nginx tag.

• Tests of this Helm chart would be more meaningful as the nginx version that is tested against is what would also be running on enduser's systems.

Possible drawbacks

• There would be an additional maintenance effor of keeping the version up-to-date in this chart.

[provokateurin]

We could also change the nginx.image.pullPolicy to Always. Either as a temporary workaround or a permanent. I agree though that we should point to a specific version, so let's do it the proper way.

[jessebot]

I second a specific version that gets updated somehow via dependabot or renovatebot. Marked as good first issue for anyone who knows helm well enough to get this done.